Microstructure and photocatalytic performance of high velocity oxy-fuel sprayed TiO2 coatings

Titanium dioxide photocatalytic coatings were deposited through high velocity oxy-fuel (HVOF) spraying agglomerate anatase powder. Different spray parameters (e.g. flow of fuel gas) were utilized with the aim to reveal their influence on microstructure and photocatalytic performance of the HVOF titania. coatings. The microstructure of the coatings was characterized using X-ray diffraction and scanning electron microscope. The photocatalytic performance of the coatings was evaluated through analyzing photocatalytical degradation of phenol using an ultraviolet spectrometry. Results showed that the phase compositions of the titania coatings were significantly influenced by melting state of the sprayed particles, which was influenced mainly by fuel gas flow. The HVOF TiO2 coating with up to 70% anatase phase can be obtained through assuring a limited melting state of the titania powder during the coating deposition. A content of 40% of the anatase phase was obtained in the coating deposited from well-melted particles. Furthermore, the present HVOF titania coatings showed promising effect in photocatalytically degrading phenol in the solution. It was found that the complete mineralization of phenol was controlled by the degradation of the intermediates resulting from the decomposition of phenol. It was also noted that the presence of certain rutile phase in the HVOF titania coatings enhanced their photocatalytic performance. (C) 2004 Elsevier B.V. All rights reserved.